Go to 1 on 1 mode and enter the second player with a Wiimote + Classic Controller. (When asked for control config, use the Pro version, aka, right one.) Then on the weapon selection, unplug the classic controller and connect the nunchuk. Now you'll find out that the controller actually responds properly to most inputs, including the Control Pad on the Wii Remote.

Controls:

Control stick = moveC = SquidZ = ShootB = Jump

Sadly, the rest of the controls including camera isn't mapped to any button. (If you choose the left button setup, regular classic controller) on when asked at the start, you get to use the subweapon but disables everything else.)

Yep. It's almost like if Nintendo was planning on implementing Nunchuk controls, but then decided against it but didn't delete the code for it.

The first thing you'll notice is that the game doesn't complain at all about a lack of Classic Controller on the Wii Remote. When you unplug it the first time, it just sends you to the Home menu, but you can press Home again to exit it. After that first time, though, it works like normal.

And another thing worth mentioning, is that, to prove this isn't some sort of bug or something, the Control Pad on the Wii Remote and all the buttons are completely disabled when the Classic Controller is plugged in. What this means is that the Nunchuk and Wii Remote button mappings were purposely programmed like that, knowing that there IS a Nunchuk connected.